With the rapid development in communication technology, the cell phone (or mobile phone) has gradually become an indispensable necessity of life. Developed and intensive communication base station network are facilitating for popularity of mobile phones. By means of the base station, mobile phones can link to a communication networks to communicate with others.
In general, base station includes femtocell and macrocell. The femtocell is referred to as a home base station with small coverage which is mainly used to cover the areas without covered by the other base station and to improve data transmission rate. It is typically used for residential or small business environment. The macrocell has more coverage for service which can provide uninterrupted service to users, but with slower transmission rate. By contrast, the femtocell has less coverage for service and discontinuously, but with faster transmission rate. Therefore, within coverage of the femtocell, it is easier using to users for transmission, to facilitate improving the transmission rate, and quality of call. As an user moves from a femtocell to another femtocell, the communication device locates within service coverage of the macrocell for a time period. In the existing mobile management mechanisms, in order to maintain uninterrupted call (conversation), the communication devices will associate with the macrocell (macro cellular base station) to establish a radio link. Generally speaking, such mechanisms are referred as to handoff or handover.
As mentioned above, when the communication device conducts voice or data services, during a femtocell moving to another femtocell, the communication device will locate within service coverage of the macrocell for a time period. Once, the macrocell currently has no extra radio resources, services being carried out by the communication devices will be forced to interrupt such that it substantially lowers user satisfaction. On the other hand, if the communication device can smoothly switch to the macrocell, the communication device may also stay in a short time, and immediately handover to the femtocell to enhance the quality of transmission. While, this situation will make communication devices to conduct high frequency of handover. Thus, it will increase the delay time caused by switching cells, which makes a serious decrease in quality of call.
To sum up, the disadvantage of these traditional handover operations, includes burden of the cost of processing, communication delay, and the communications disconnection and many other shortcomings. When the cells number increases, the frequency of handover operations of each cell will also increase, as seriously, even leading to communication networks shut down. Therefore, it is a very important key point to the development of network communications that how to design an effective handover management mechanism to reduce the probability of dropped calls, reduce the delay time as required frequency by switching cells and increase the overall capacity of network services.